Add Authority Advisory AI and API Lifecycle Configuration

- Introduced AuthorityAdvisoryAiOptions and related classes for managing advisory AI configurations, including remote inference options and tenant-specific settings.
- Added AuthorityApiLifecycleOptions to control API lifecycle settings, including legacy OAuth endpoint configurations.
- Implemented validation and normalization methods for both advisory AI and API lifecycle options to ensure proper configuration.
- Created AuthorityNotificationsOptions and its related classes for managing notification settings, including ack tokens, webhooks, and escalation options.
- Developed IssuerDirectoryClient and related models for interacting with the issuer directory service, including caching mechanisms and HTTP client configurations.
- Added support for dependency injection through ServiceCollectionExtensions for the Issuer Directory Client.
- Updated project file to include necessary package references for the new Issuer Directory Client library.

src/Concelier/StellaOps.Concelier.WebService/Program.cs

@@ -101,6 +101,7 @@ builder.Services.AddSingleton<IAdvisoryObservationQueryService, AdvisoryObservat
 builder.Services.AddMergeModule(builder.Configuration);
 builder.Services.AddJobScheduler();
 builder.Services.AddBuiltInConcelierJobs();
+builder.Services.AddSingleton<OpenApiDiscoveryDocumentProvider>();
 
 builder.Services.AddSingleton<ServiceStatus>(sp => new ServiceStatus(sp.GetRequiredService<TimeProvider>()));
 builder.Services.AddAocGuard();
@@ -209,6 +210,50 @@ if (resolvedAuthority.Enabled && resolvedAuthority.AllowAnonymousFallback)
 
 app.MapConcelierMirrorEndpoints(authorityConfigured, enforceAuthority);
 
+app.MapGet("/.well-known/openapi", (OpenApiDiscoveryDocumentProvider provider, HttpContext context) =>
+{
+    var (payload, etag) = provider.GetDocument();
+
+    if (context.Request.Headers.IfNoneMatch.Count > 0)
+    {
+        foreach (var candidate in context.Request.Headers.IfNoneMatch)
+        {
+            if (Matches(candidate, etag))
+            {
+                context.Response.Headers.ETag = etag;
+                context.Response.Headers.CacheControl = "public, max-age=300, immutable";
+                return Results.StatusCode(StatusCodes.Status304NotModified);
+            }
+        }
+    }
+
+    context.Response.Headers.ETag = etag;
+    context.Response.Headers.CacheControl = "public, max-age=300, immutable";
+    return Results.Text(payload, "application/vnd.oai.openapi+json;version=3.1");
+    
+    static bool Matches(string? candidate, string expected)
+    {
+        if (string.IsNullOrWhiteSpace(candidate))
+        {
+            return false;
+        }
+
+        var trimmed = candidate.Trim();
+        if (string.Equals(trimmed, expected, StringComparison.Ordinal))
+        {
+            return true;
+        }
+
+        if (trimmed.StartsWith("W/", StringComparison.OrdinalIgnoreCase))
+        {
+            var weakValue = trimmed[2..].TrimStart();
+            return string.Equals(weakValue, expected, StringComparison.Ordinal);
+        }
+
+        return false;
+    }
+}).WithName("GetConcelierOpenApiDocument");
+
 var jsonOptions = new JsonSerializerOptions(JsonSerializerDefaults.Web);
 jsonOptions.Converters.Add(new JsonStringEnumConverter());